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dhcp.c File Reference
Functions | Variables

dhcp.c File Reference

Dynamic Host Configuration Protocol client. More...

Go to the source code of this file.

Functions

static err_t dhcp_discover (struct netif *netif)
 Start the DHCP process, discover a DHCP server.
static err_t dhcp_select (struct netif *netif)
 Select a DHCP server offer out of all offers.
static void dhcp_bind (struct netif *netif)
 Bind the interface to the offered IP address.
static err_t dhcp_decline (struct netif *netif)
 Decline an offered lease.
static err_t dhcp_rebind (struct netif *netif)
 Rebind with a DHCP server for an existing DHCP lease.
static err_t dhcp_reboot (struct netif *netif)
 Enter REBOOTING state to verify an existing lease.
static void dhcp_recv (void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port)
 If an incoming DHCP message is in response to us, then trigger the state machine.
static void dhcp_timeout (struct netif *netif)
 A DHCP negotiation transaction, or ARP request, has timed out.
static void dhcp_t1_timeout (struct netif *netif)
 The renewal period has timed out.
static void dhcp_t2_timeout (struct netif *netif)
 The rebind period has timed out.
static err_t dhcp_create_msg (struct netif *netif, struct dhcp *dhcp, u8_t message_type)
 Create a DHCP request, fill in common headers.
static void dhcp_delete_msg (struct dhcp *dhcp)
 Free previously allocated memory used to send a DHCP request.
static void dhcp_option_trailer (struct dhcp *dhcp)
 Add a DHCP message trailer.
static void dhcp_handle_nak (struct netif *netif)
 Back-off the DHCP client (because of a received NAK response).
static void dhcp_check (struct netif *netif)
 Checks if the offered IP address is already in use.
static void dhcp_handle_offer (struct netif *netif)
 Remember the configuration offered by a DHCP server.
void dhcp_coarse_tmr ()
 The DHCP timer that checks for lease renewal/rebind timeouts.
void dhcp_fine_tmr ()
 DHCP transaction timeout handling.
static void dhcp_handle_ack (struct netif *netif)
 Handle a DHCP ACK packet.
void dhcp_set_struct (struct netif *netif, struct dhcp *dhcp)
 Set a statically allocated struct dhcp to work with.
err_t dhcp_start (struct netif *netif)
 Start DHCP negotiation for a network interface.
void dhcp_inform (struct netif *netif)
 Inform a DHCP server of our manual configuration.
void dhcp_network_changed (struct netif *netif)
 Handle a possible change in the network configuration.
void dhcp_arp_reply (struct netif *netif, ip_addr_t *addr)
 Match an ARP reply with the offered IP address.
err_t dhcp_renew (struct netif *netif)
 Renew an existing DHCP lease at the involved DHCP server.
err_t dhcp_release (struct netif *netif)
 Release a DHCP lease.
void dhcp_stop (struct netif *netif)
 Remove the DHCP client from the interface.
static err_t dhcp_parse_reply (struct dhcp *dhcp, struct pbuf *p)
 Extract the DHCP message and the DHCP options.

Variables

u32_t dhcp_rx_options_val [DHCP_OPTION_IDX_MAX]
 Holds the decoded option values, only valid while in dhcp_recv.
u8_t dhcp_rx_options_given [DHCP_OPTION_IDX_MAX]
 Holds a flag which option was received and is contained in dhcp_rx_options_val, only valid while in dhcp_recv.

Detailed Description

Dynamic Host Configuration Protocol client.

Definition in file dhcp.c.

Function Documentation

void dhcp_arp_reply ( struct netif *  netif,
ip_addr_t *  addr 
)

Match an ARP reply with the offered IP address.

if enabled, check whether the offered IP address is not in use, using ARP

Parameters:
netifthe network interface on which the reply was received
addrThe IP address we received a reply from

Definition at line 779 of file dhcp.c.

static void dhcp_bind ( struct netif *  netif ) [static]

Bind the interface to the offered IP address.

Parameters:
netifnetwork interface to bind to the offered address

Definition at line 903 of file dhcp.c.

static void dhcp_check ( struct netif *  netif ) [static]

Checks if the offered IP address is already in use.

It does so by sending an ARP request for the offered address and entering CHECKING state. If no ARP reply is received within a small interval, the address is assumed to be free for use by us.

Parameters:
netifthe netif under DHCP control

Definition at line 211 of file dhcp.c.

void dhcp_coarse_tmr ( void   )

The DHCP timer that checks for lease renewal/rebind timeouts.

to be called every minute

Definition at line 333 of file dhcp.c.

static err_t dhcp_create_msg ( struct netif *  netif,
struct dhcp *  dhcp,
u8_t  message_type 
) [static]

Create a DHCP request, fill in common headers.

Parameters:
netifthe netif under DHCP control
dhcpdhcp control struct
message_typemessage type of the request

default global transaction identifier starting value (easy to match with a packet analyser). We simply increment for each new request. Predefine DHCP_GLOBAL_XID to a better value or a function call to generate one at runtime, any supporting function prototypes can be defined in DHCP_GLOBAL_XID_HEADER

Definition at line 1601 of file dhcp.c.

static err_t dhcp_decline ( struct netif *  netif ) [static]

Decline an offered lease.

Tell the DHCP server we do not accept the offered address. One reason to decline the lease is when we find out the address is already in use by another host (through ARP).

Parameters:
netifthe netif under DHCP control

Definition at line 808 of file dhcp.c.

static void dhcp_delete_msg ( struct dhcp *  dhcp ) [static]

Free previously allocated memory used to send a DHCP request.

Parameters:
dhcpthe dhcp struct to free the request from

Definition at line 1689 of file dhcp.c.

static err_t dhcp_discover ( struct netif *  netif ) [static]

Start the DHCP process, discover a DHCP server.

Parameters:
netifthe netif under DHCP control

Definition at line 848 of file dhcp.c.

void dhcp_fine_tmr ( void   )

DHCP transaction timeout handling.

to be called every half second

A DHCP server is expected to respond within a short period of time. This timer checks whether an outstanding DHCP request is timed out.

Definition at line 365 of file dhcp.c.

static void dhcp_handle_ack ( struct netif *  netif ) [static]

Handle a DHCP ACK packet.

Parameters:
netifthe netif under DHCP control

Definition at line 504 of file dhcp.c.

static void dhcp_handle_nak ( struct netif *  netif ) [static]

Back-off the DHCP client (because of a received NAK response).

Back-off the DHCP client because of a received NAK. Receiving a NAK means the client asked for something non-sensible, for example when it tries to renew a lease obtained on another network.

We clear any existing set IP address and restart DHCP negotiation afresh (as per RFC2131 3.2.3).

Parameters:
netifthe netif under DHCP control

Definition at line 183 of file dhcp.c.

static void dhcp_handle_offer ( struct netif *  netif ) [static]

Remember the configuration offered by a DHCP server.

Parameters:
netifthe netif under DHCP control

Definition at line 238 of file dhcp.c.

void dhcp_inform ( struct netif *  netif )

Inform a DHCP server of our manual configuration.

inform server of our manual IP address

This informs DHCP servers of our fixed IP address configuration by sending an INFORM message. It does not involve DHCP address configuration, it is just here to be nice to the network.

Parameters:
netifThe lwIP network interface

Definition at line 691 of file dhcp.c.

void dhcp_network_changed ( struct netif *  netif )

Handle a possible change in the network configuration.

This enters the REBOOTING state to verify that the currently bound address is still valid.

Definition at line 745 of file dhcp.c.

static void dhcp_option_trailer ( struct dhcp *  dhcp ) [static]

Add a DHCP message trailer.

Adds the END option to the DHCP message, and if necessary, up to three padding bytes.

Parameters:
dhcpDHCP state structure

Definition at line 1710 of file dhcp.c.

static err_t dhcp_parse_reply ( struct dhcp *  dhcp,
struct pbuf *  p 
) [static]

Extract the DHCP message and the DHCP options.

Extract the DHCP message and the DHCP options, each into a contiguous piece of memory. As a DHCP message is variable sized by its options, and also allows overriding some fields for options, the easy approach is to first unfold the options into a conitguous piece of memory, and use that further on.

Definition at line 1304 of file dhcp.c.

static err_t dhcp_rebind ( struct netif *  netif ) [static]

Rebind with a DHCP server for an existing DHCP lease.

Parameters:
netifnetwork interface which must rebind with a DHCP server

Definition at line 1056 of file dhcp.c.

static err_t dhcp_reboot ( struct netif *  netif ) [static]

Enter REBOOTING state to verify an existing lease.

Parameters:
netifnetwork interface which must reboot

Definition at line 1116 of file dhcp.c.

static void dhcp_recv ( void *  arg,
struct udp_pcb *  pcb,
struct pbuf *  p,
ip_addr_t *  addr,
u16_t  port 
) [static]

If an incoming DHCP message is in response to us, then trigger the state machine.

Definition at line 1497 of file dhcp.c.

err_t dhcp_release ( struct netif *  netif )

Release a DHCP lease.

release the DHCP lease, usually called before dhcp_stop()

Parameters:
netifnetwork interface which must release its lease

Definition at line 1158 of file dhcp.c.

err_t dhcp_renew ( struct netif *  netif )

Renew an existing DHCP lease at the involved DHCP server.

enforce early lease renewal (not needed normally)

Parameters:
netifnetwork interface which must renew its lease

Definition at line 993 of file dhcp.c.

static err_t dhcp_select ( struct netif *  netif ) [static]

Select a DHCP server offer out of all offers.

Simply select the first offer received.

Parameters:
netifthe netif under DHCP control
Returns:
lwIP specific error (see error.h)

Definition at line 269 of file dhcp.c.

void dhcp_set_struct ( struct netif *  netif,
struct dhcp *  dhcp 
)

Set a statically allocated struct dhcp to work with.

Using this prevents dhcp_start to allocate it using mem_malloc.

Parameters:
netifthe netif for which to set the struct dhcp
dhcp(uninitialised) dhcp struct allocated by the application

Definition at line 583 of file dhcp.c.

err_t dhcp_start ( struct netif *  netif )

Start DHCP negotiation for a network interface.

start DHCP configuration

If no DHCP client instance was attached to this interface, a new client is created first. If a DHCP client instance was already present, it restarts negotiation.

Parameters:
netifThe lwIP network interface
Returns:
lwIP error code
  • ERR_OK - No error
  • ERR_MEM - Out of memory

Definition at line 608 of file dhcp.c.

void dhcp_stop ( struct netif *  netif )

Remove the DHCP client from the interface.

stop DHCP configuration

Parameters:
netifThe network interface to stop DHCP on

Definition at line 1210 of file dhcp.c.

static void dhcp_t1_timeout ( struct netif *  netif ) [static]

The renewal period has timed out.

Parameters:
netifthe netif under DHCP control

Definition at line 461 of file dhcp.c.

static void dhcp_t2_timeout ( struct netif *  netif ) [static]

The rebind period has timed out.

Parameters:
netifthe netif under DHCP control

Definition at line 483 of file dhcp.c.

static void dhcp_timeout ( struct netif *  netif ) [static]

A DHCP negotiation transaction, or ARP request, has timed out.

The timer that was started with the DHCP or ARP request has timed out, indicating no response was received in time.

Parameters:
netifthe netif under DHCP control

Definition at line 398 of file dhcp.c.

Variable Documentation

u8_t dhcp_rx_options_given[DHCP_OPTION_IDX_MAX]

Holds a flag which option was received and is contained in dhcp_rx_options_val, only valid while in dhcp_recv.

Definition at line 127 of file dhcp.c.

u32_t dhcp_rx_options_val[DHCP_OPTION_IDX_MAX]

Holds the decoded option values, only valid while in dhcp_recv.

Definition at line 123 of file dhcp.c.

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